The present invention relates to an apparatus for explosive severing of tubular members and more specifically to an apparatus for severing tubular members below a body of water, such as for example an offshore rig platform pile.
During offshore drilling and production operations, it becomes necessary to move a platform to a different location or to permanently move the platform away from that particular sea area.
Since an offshore platform is oftentimes supported by a number of piles which extend from the platform downwardly through the body of water and below a mud line, there exists a problem of removing those piles or at least part of the piles, so as to allow unencumbered navigation in the area where the platform has been deployed.
The current environmental protection laws require that the piles which have supported the platform be severed at least 15 feet below the mud line.
As is often the case, the pile becomes clogged with mud if any substantial period of time has passed since the platform was removed until the time when the pile is eventually severed and removed. The mud from the pile has to be evacuated before the explosive device can be positioned inside the pile at a predetermined depth for severing the pile and removing the severed part from the bottom of the ocean.
The traditionally used method utilizes a sparging apparatus which is used for delivery of air and water under pressure from an equipment positioned on a barge at the location, wherein the piles need to be removed. The sparging apparatus is lowered by a crane positioned on the barge into the open top end of the pile and the air and water are introduced, under pressure, into the sparging nozzle, so as to break the mud and force it outwardly from the pile to prepare the space for deployment of an explosive pile severing device. As the practice showed, the mud which has been agitated by the sparging apparatus is mostly evacuated from the pile, with still an unacceptable amount of it falling back into the pile and further intervening with the mud evacuation process. As a result, considerable time is lost for evacuation of the mud to a depth wherein the explosive device must be positioned within the pile. Additional drawback is associated with the fact that the sparging device, being lowered in the water, has to be positioned with precision to enter the narrow open top of the pile, which causes sometimes damage to the sparging device, which in turn translates into the loss of valuable time.
The present invention contemplates elimination of the drawbacks associated with the prior art and provision of the explosive device for severing tubular members, such as underwater piles, which have been filled with mud or silt.